- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
A new approach to correlate the defect population with the fatigue life of selective laser melted Ti-6Al-4V alloy
摘要： Microstructural features and defects arising from selective laser melting (SLM) determine the in-service performance of additively manufactured near-net-shape components. Here the grain type, shape, size and distribution were characterized using electron backscattered diffraction (EBSD). High-resolution synchrotron radiation X-ray computed tomography was used to quantify the population, morphology and dimensions of porosity and lack of fusion defects. For SLM Ti-6Al-4V alloy, the larger-sized defects in comparison with α′ grains are more important for crack initiation, typically leading to poor fatigue resistance and a pronounced variation in fatigue life. The fatigue strength was then evaluated in terms of the defect population using a combination of the statistics of extremes and the Murakami model. Finally, an extended Kitagawa-Takahashi fatigue diagram was established within the framework of defect-tolerant design, which includes a classical safe-life region and the defect-determined lifetime in the finite life region.
关键词： Defect tolerance assessment,Chapetti model,Fatigue crack initiation and propagation,Kitagawa-Takahashi diagram,Additive manufacturing
更新于2025-09-19 17:13:59
-
In-situ optical emission spectroscopy of selective laser melting
摘要： The variances in local processing conditions during Selective Laser Melting (SLM), a powder bed Additive Manufacturing (AM) process, can cause defects that lead to part failure. The nature of SLM permits in-situ monitoring of radiometric signals emitted from the part surface during the process, including optical emission from excited alloying elements. Using Optical Emission Spectroscopy (OES) to measure the spectral content of light emitted gives insight into the chemistry and relative intensities of excited species vaporized during SLM processing. The contribution from investigating the use of in-situ OES to gain information about local processing conditions during SLM is reported in this paper. A spectrometer is split into the SLM system laser beam path to measure visible light emitted from the melt pool and plume during the processing of 304L stainless steel. The in-line configuration allows signal collection regardless of the laser scan location. The spectroscopic information is correlated to the melt pool size and features of SLM samples for various build conditions (i.e., process parameters, build chamber atmosphere type, and pressure).The limitations that exist in OES implementation for certain build chamber conditions are discussed. The results in this paper are initial progress towards the use of OES in SLM part qualification and controls applications.
关键词： Metal additive manufacturing,Optical emission spectroscopy,In-situ monitoring,Powder bed fusion
更新于2025-09-19 17:13:59
-
Development and calibration of a CFD-based model of the bed fusion SLM additive manufacturing process aimed at optimising laser parameters
摘要： The main concern deriving from the Selective Laser Melting technique is attaining a fully dense part out of the interconnected tracks. The right choice of process parameters is of fundamental importance to get a porosity free component. In this work a model has been developed simulating the printing process with the aim of creating a simple numerical tool for designing processing windows suitable to metal alloys of any composition. The applied simplified approach makes the model use as much practical as possible, while keeping the physical description representative. The model has been calibrated fitting experimental measures of track width, depth and cross sectional area taken from three literature sources, referring to: Ti6Al4V, Inconel 625 and Al7050. Effective liquid pool thermal conductivity, laser absorptivity and depth of application of laser energy are the fitting parameters. Laser absorptivity and depth of application of laser energy result to rise almost linearly with increasing specific energy; the slopes of the three analyzed alloys result very close to each other. The obtained results give confidence about the possibility of using the model as a predicting tool after further calibration on a wider range of metal alloys.
关键词： laser parameters,numerical model,processing window,SLM,additive manufacturing,metal alloys
更新于2025-09-19 17:13:59
-
Investigation of Laser Polishing of Four Selective Laser Melting Alloy Samples
摘要： Selective laser melting (SLM) is a layer by layer process of melting and solidifying of metal powders. The surface quality of the previous layer directly affects the uniformity of the next layer. If the surface roughness value of the previous layer is large, there is the possibility of not being able to complete the layering process such that the entire process has to be abandoned. At least, it may result in long term durability problem and the inhomogeneity, may even make the processed structure not be able to be predicted. In the present study, the ability of a fiber laser to in-situ polish the rough surfaces of four typical additive-manufactured alloys, namely, Ti6Al4V, AlSi10Mg, 316L and IN718 was demonstrated. The results revealed that the surface roughness of the as-received alloys could be reduced to about 3 μm through the application of the laser-polishing process, and the initial surfaces had roughness values of 8.80–16.64 μm. Meanwhile, for a given energy density, a higher laser power produced a laser-polishing effect that was often more obvious, with the surface roughness decreasing with an increase in the laser power. Further, the polishing strategy will be optimized by simulation in our following study.
关键词： laser polishing,additive manufacturing,selective laser melting,typical alloys,surface roughness
更新于2025-09-19 17:13:59
-
Reconfigurable H‐plane waveguide phase shifters prototyping with additive manufacturing at K‐band
摘要： This work presents the design and manufacturing of a K-band reconfigurable phase shifter completely implemented in waveguide technology for reduced insertion loss, good matching, and large phase shifting range. The device is based on the combination of a short slot coupler and two tunable reactive loads implemented as a section of short-circuited waveguide where an adjustable metallic post is inserted. Three prototypes of this design have been manufactured using different techniques (conventional computer numerical control machining, a low-cost fused filament fabrication technique and direct metal laser sintering) in order to assess its performance for different applications. The prototypes have been characterized experimentally and the achieved results are evaluated and compared. The proposed phase shifter, since it is fully developed in waveguide technology, eliminates the need of adding transitions to planar structures in order to integrate lumped components like pin diodes or varactors. Therefore, this device has a great potential in high-power beam steering phased arrays.
关键词： reconfigurable,selective laser sintering,additive manufacturing,waveguide,fused filament fabrication,phase shifter
更新于2025-09-19 17:13:59
-
Laser Beam Polishing of Polymers
摘要： Fused layer manufacturing (FLM) is an additive manufacturing process in which parts are built in layers by localized extrusion of molten polymer through a nozzle. It offers a high degree of geometrical flexibility as well as a wide range of suitable materials. Unfortunately, a characteristically high surface roughness is limiting the number of possible applications. The following article provides investigations regarding the remelting of FLM surfaces via laser beam polishing as an effective method for achieving a reduced roughness.
关键词： FLM-printed parts,polymers,laser beam polishing,surface roughness,additive manufacturing
更新于2025-09-19 17:13:59
-
Laser Polishing of Ti6Al4V Fabricated by Selective Laser Melting
摘要： Selective laser melting (SLM) is emerging as a promising 3D printing method for orthopedic and dental applications. However, SLM-based Ti6Al4V components frequently exhibit high roughness values and partial surface defects. Laser polishing (LP) is a newly developed technology to improve the surface quality of metals. In this research, LP is applied to improve the surface ?nish of components. The results show that the laser beam can neatly ablate the aggregates of metallic globules and repair cracks and pores on the surface, resulting in a smooth surface with nanocomposites. Overall, the results indicate that using LP optimizes surface morphology to favor fatigue behavior and osteoblastic di?erentiation. These ?ndings provide foundational data to improve the surface roughness of a laser-polished implant and pave the way for optimized mechanical behavior and biocompatibility via the laser process.
关键词： laser polishing,additive manufacturing,biocompatibility,mechanical properties,surface roughness
更新于2025-09-19 17:13:59
-
Transferability of Process Parameters in Laser Powder Bed Fusion Processes for an Energy and Cost Efficient Manufacturing
摘要： In the past decade, the sales of metal additive manufacturing systems have increased intensely. In particular, PBF-LB/M systems (powder bed fusion of metals using a laser-based system) represent a technology of great industrial interest, in which metallic powders are molten and solidified layer upon layer by a focused laser beam. This leads to a simultaneous increase in demand for metallic powder materials. Due to adjusted process parameters of PBF-LB/M systems, the powder is usually procured by the system’s manufacturer. The requirement and freedom to process different feedstocks in a reproducible quality and the economic and ecological factors involved are reasons to have a closer look at the differences between the quality of the provided metallic powders. Besides, different feedstock materials require different energy inputs, allowing a sustainable process control to be established. In this work, powder quality of stainless steel 1.4404 and the effects during the processing of metallic powders that are nominally the same were analyzed and the influence on the build process followed by the final part quality was investigated. Thus, a correlation between morphology, particle size distribution, absorptivity, flowability, and densification depending on process parameters was demonstrated. Optimized exposure parameters to ensure a more sustainable and energy and cost-efficient manufacturing process were determined.
关键词： powder characterization,stainless steel (1.4404; 316L),energy and cost-efficient manufacturing,PBF-LB/M,sustainable process parameters,additive manufacturing
更新于2025-09-16 10:30:52
-
Direct fabrication mechanism of pre-sintered Si3N4 ceramic with ultra-high porosity by laser additive manufacturing
摘要： Complex structural Si3N4 ceramics with ultra-high porosity were innovatively formed by selective laser sintering (SLS) technology without any binder. Due to rapid cooling rate, the high temperature phase constituent and microstructure of the SLSed Si3N4 poly hollow microspheres (PHMS) were preserved, thus revealing the bonding mechanism of Si3N4 under the nonequilibrium heat source. Si3N4 PHMS are bonded by microvilli composed of bamboo-structure SiO2 nano?ber clusters, stacked SiO2 nanospheres and smooth α-Si3.72N4 nanowires. Finally, the pre-sintered Si3N4 ceramics with a porosity of 80% are directly fabricated in the atmosphere by SLS, which have the enough strength to satisfy the post-treatment requirements.
关键词： Bonding mechanism,Selective laser sintering,Additive manufacturing,Nanostructure,Silicon nitride
更新于2025-09-16 10:30:52
-
Microstructure and fatigue behavior of a laser additive manufactured 12CrNi2 low alloy steel
摘要： In this research, 12CrNi2 low alloy steel was successfully prepared by laser melting deposition (LMD). The mechanisms driving high cycle fatigue fracture of the as-built LMD 12CrNi2 low alloy steel were investigated and a concurrent process-microstructure-property relationship was established through microstructural analysis. The results showed that the crystal structures of the as-built LMD 12CrNi2 steel mainly consisted of the ferrite and a small amount of Cr23C6 carbides. No preferred texture was observed as a result of the complicated heat flux direction during fabrication. Based on the examination of the fracture surface, fatigue cracks of the as-built LMD 12CrNi2 steel initiated from subsurface defects for all the cases. Crack propagation zones showed a mixed mode of transgranular and intergranular fracture in a brittle manner, whereas the final fracture zones displayed dimples typical of ductile fracture. The kernel average misorientation (KAM) map indicated that the strain localization predominantly occurred at the grain boundaries and slightly appeared at the interior of the ferrite grains. Schmid factor distribution results implied that fatigue cracks originated from grains with {123}<111> slip system due to the prior activation of {123}<111> slip system.
关键词： Fractography,High cycle fatigue,Microstructure,12CrNi2 low alloy steel,Laser additive manufacturing
更新于2025-09-16 10:30:52